It is well-known that threaded couplings are effective under restricted space conditions where the vertical space available for coupling an object is limited. In the conventional screw-type couplings designed for use under such restricted space conditions, a lamellar screw or discontinuous screw formed from a lamellar block by a drill press or similar means was used only for the female or internal threaded member. Since the flight depth of the internal thread is the same as that of the ordinary angular screws, the pressure-carrying contact area between both internal and external threads, which is directly effective for screw fixing, was very limited, and hence there arose a possibility of disengagement or improper engagement of threads due to tension load or bending load or loosening of thread engagement due to vibrating loads. This jeopardized or prevented the secure fixing of the object. Also, if a separate attachment fitting such as a washer is provided for detent means, it could become impossible to conform the entire assembly to the restricted space condition such as above-mentioned. It is also apparent that the above- problems can not be corrected if an ordinary angular thread is used for both of the internal and external threaded members. Further, the use of other securing techniques such as rivetting involves the need for specific tool (or tools) or highly skilled technique for maintenance, inspection, repair and detachment when such are required.
It is an object of the present invention to provide a screw-type coupling for fixing an object in a desired position, and more particularly to a threaded coupling of the discontinuous type.
An object of the present invention is to provide a threaded coupling of the character described which permits utilization of an increased pressure-sustaining area for threading while conforming to the requirements of the restricted space conditions such as aforementiond.
Another object of the present invention is to provide a threaded coupling which can be operated with ease even by an inexperienced person with a single commonly used screw driver as the only operating tool.
Still another object of the present invention is to provide a threaded coupling which necessitates no separate detent means.